=pod

=head1 NAME

genpkey - generate a private key

=head1 SYNOPSIS

B<openssl> B<genpkey>
[B<-out filename>]
[B<-outform PEM|DER>]
[B<-pass arg>]
[B<-cipher>]
[B<-engine id>]
[B<-paramfile file>]
[B<-algorithm alg>]
[B<-pkeyopt opt:value>]
[B<-genparam>]
[B<-text>]

=head1 DESCRIPTION

The B<genpkey> command generates a private key.

=head1 OPTIONS

=over 4

=item B<-out filename>

the output filename. If this argument is not specified then standard output is
used.  

=item B<-outform DER|PEM>

This specifies the output format DER or PEM.

=item B<-pass arg>

the output file password source. For more information about the format of B<arg>
see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.

=item B<-cipher>

This option encrypts the private key with the supplied cipher. Any algorithm
name accepted by EVP_get_cipherbyname() is acceptable such as B<des3>.

=item B<-engine id>

specifying an engine (by it's unique B<id> string) will cause B<req>
to attempt to obtain a functional reference to the specified engine,
thus initialising it if needed. The engine will then be set as the default
for all available algorithms. If used this option should precede all other
options.

=item B<-algorithm alg>

public key algorithm to use such as RSA, DSA or DH. If used this option must
precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
are mutually exclusive.

=item B<-pkeyopt opt:value>

set the public key algorithm option B<opt> to B<value>. The precise set of
options supported depends on the public key algorithm used and its
implementation. See B<KEY GENERATION OPTIONS> below for more details.

=item B<-genparam>

generate a set of parameters instead of a private key. If used this option must
precede and B<-algorithm>, B<-paramfile> or B<-pkeyopt> options.

=item B<-paramfile filename>

Some public key algorithms generate a private key based on a set of parameters.
They can be supplied using this option. If this option is used the public key
algorithm used is determined by the parameters. If used this option must
precede and B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
are mutually exclusive.

=item B<-text>

Print an (unencrypted) text representation of private and public keys and
parameters along with the PEM or DER structure.

=back

=head1 KEY GENERATION OPTIONS

The options supported by each algorith and indeed each implementation of an
algorithm can vary. The options for the OpenSSL implementations are detailed
below.

=head1 RSA KEY GENERATION OPTIONS

=over 4

=item B<rsa_keygen_bits:numbits>

The number of bits in the generated key. If not specified 1024 is used.

=item B<rsa_keygen_pubexp:value>

The RSA public exponent value. This can be a large decimal or
hexadecimal value if preceded by B<0x>. Default value is 65537.

=back

=head1 DSA PARAMETER GENERATION OPTIONS

=over 4

=item B<dsa_paramgen_bits:numbits>

The number of bits in the generated parameters. If not specified 1024 is used.

=head1 DH PARAMETER GENERATION OPTIONS

=over 4

=item B<dh_paramgen_prime_len:numbits>

The number of bits in the prime parameter B<p>.

=item B<dh_paramgen_generator:value>

The value to use for the generator B<g>.

=back

=head1 EC PARAMETER GENERATION OPTIONS

=over 4

=item B<ec_paramgen_curve:curve>

the EC curve to use.

=back

=head1 NOTES

The use of the genpkey program is encouraged over the algorithm specific
utilities because additional algorithm options and ENGINE provided algorithms
can be used.

=head1 EXAMPLES

Generate an RSA private key using default parameters:

 openssl genpkey -algoritm RSA -out key.pem 

Encrypt output private key using 128 bit AES and the passphrase "hello":

 openssl genpkey -algoritm RSA -out key.pem -aes-128-cbc -pass pass:hello

Generate a 2048 bit RSA key using 3 as the public exponent:

 openssl genpkey -algoritm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048 \
 						-pkeyopt rsa_keygen_pubexp:3

Generate 1024 bit DSA parameters:

 openssl genpkey -genparam -algorithm DSA -out dsap.pem \
						-pkeyopt dsa_paramgen_bits:1024

Generate DSA key from parameters:

 openssl genpkey -paramfile dsap.pem -out dsakey.pem 

Generate 1024 bit DH parameters:

 openssl genpkey -genparam -algorithm DH -out dhp.pem \
					-pkeyopt dh_paramgen_prime_len:1024

Generate DH key from parameters:

 openssl genpkey -paramfile dhp.pem -out dhkey.pem 


=cut